I have a 2007 Toyota Corolla Sport that usually runs really smooth. About a month back something came loose which made the speedometer stop working. I took it in and it was an easy fix. Since then I've noticed it feels a bit rough. It's really hard to explain--almost like when I'm idling and then push on the gas pedal or when I'm going slow and speed up quickly (like merging onto the freeway) it's almost like there's a 1 second delay before it reves and takes off. What could this be?